The present invention pertains to latent, self-curing epoxy resin compositions.
Amine-substituted aromatic sulfonic acid amides disclosed by Pettigrew in U.S. Pat. No. 3,277,050 to be suitable curing agents for epoxy resins. Godfrey and Schulze in U.S. Pat. No. 3,591,556 disclose the curing of epoxy resins with a combination of sulfonamides and polyoxyalkylene polyamines. Stoy and Roth in U.S. Pat. No. 3,899,546 disclose compositions which comprise (A) an interpolymer of an aldehyde and amine substituted aromatic sulfonic acid amide, (B) an epoxy resin and (C) a curing agent.
Because of the poor solubility of the sulfonamides employed in the aforementioned patents, coating formulations and the like requiring high solids content and relatively low application vicosities at low temperatures are not practical. The present invention provides a method for employing such sulfonamides as curing agents by prereacting, without curing to a thermoset condition, the sulfonamide with an epoxy resin thereby producing a latent self-curing epoxy resin which is capable of being employed in high solids applications with suitable viscosities at low temperatures. Curing, however, is accomplished at a relatively high temperature.